Looking to digitise some VHS tapes, so am looking for some old video capture cards, but not sure if they will work with Windows 7 or Linux - can't find the information online, so am hoping someone here can tell me...

The capture cards you are asking about were designed to work with Windows XP. The most likely reason that you could not find Windows 7 drivers available for them is that Pinnacle abandoned them years ago. Pinnacle has been sold and re-sold since those cards were released and likely those in charge decided that was continuing support for them after Windows 7 arrived was not worthwhile.

If you know the chipset e.g. bt848, BT878. bt878a etc... you may be able to use generic drivers. I haven't used them except on xp but a Google search with those codes or "Conexant" and window 7 or 8 (and possible 32 or 64 bit) will show some claiming 64 bit drivers are available. Caution... as with many Google driver search results some links lead to "driver search/download programs" instead of the driver file itself. I found a rar file for bt848 drivers but since I haven't tested it I won't post the link. They shouldn't be too hard to find. This is all I put in the Google search "generic bt878 64 bit drivers for window 7". Whether they work or not above XP I can't say for sure. You could try the same search with Linux but it could be hit and miss. I did see some threads where people said the old bt878 cards work. I successfully tested the generic drivers with Linux but that was a few years ago there may may issues with newer versions of Linux.

If you already own the card it wouldn't hurt to try but you can buy a pretty cheap usb capture device that can capture from multiple digital and analog sources.

I agree. There are at least a couple of current decent and relatively inexpensive USB capture devices that would work well for capturing video with both Windows 7 and Linux. I found a review on Amazon indicating the Hauppauge USB Live 2 works with Ubuntu 12.04, and another on Amazon indicating there are Linux drivers for the EZCAP.TV 116